1. Field of the Invention
This invention relates in general to magnetic sensors, and more particularly to a method for providing an endpoint layer for ion milling of top of read sensor having top lead connection and sensor formed thereby.
2. Description of Related Art
Magnetic recording is a key and invaluable segment of the information-processing industry. While the basic principles are one hundred years old for early tape devices, and over forty years old for magnetic hard disk drives, an influx of technical innovations continues to extend the storage capacity and performance of magnetic recording products. For hard disk drives, the areal density or density of written data bits on the magnetic medium has increased by a factor of more than two million since the first disk drive was applied to data storage. Areal density continues to grow due to improvements in magnet recording heads, media, drive electronics, and mechanics.
The use of a magnetoresistive (MR) and giant magnetoresistive (GMR) sensors to sense magnetically recorded data has been known for many years. The GMR sensor includes a spin-valve film that provides a high magnetoresistance ratio (MR ratio) as compared with a conventional MR head. The MR ratio is the percentage change in resistance as an external magnetic field is switched between high and low values.
Recently, in order to satisfy the demand for higher recording density in an HDD apparatus, higher sensitivity and larger output of a thin-film magnetic head are required. A tunnel magnetoresistive effect (TMR) element and a Current-Perpendicular-To-Plane (CPP) GMR element meet these requirements and are beginning to receive attention. The TMR element utilizes a ferromagnetic tunnel effect and has a multi-layered structure including a lower ferromagnetic thin-film layer, a tunnel barrier layer and an upper ferromagnetic thin-film layer. The CPP GMR element is one type of GMR element of a multi-layered structure including a lower ferromagnetic thin-film layer, a nonmagnetic metal layer and an upper ferromagnetic thin-film layer.
These elements not only offer MR ratios several times greater than that of a general GMR element such as CIP (Current-In-Plane) GMR element in which a current flows along the surface of layers, but also implements narrow gaps between layers without difficulty. The terms “lower” in “lower ferromagnetic thin-film layer” and “upper” in “upper ferromagnetic thin-film layer” are selectively used depending on the position of the layer relative to the substrate. In general, a layer is “lower” if this layer is close to the substrate, and “upper” if the layer is away from the substrate.
In the fabrication of a CPP read sensor, the sensor is electrically connected to the top shield (S2). Prior to depositing the S2 layer, the top of the read sensor has to be etched in order to make a good electrical contact between the sensor and S2. Often the sensor capping material that has to be etched is a slow etching material, such as tantalum (Ta). A capping material such as Ta also would have an oxide layer of variable thickness.
The etching of the capping material has to be well controlled. If the etching of the capping material is not well controlled, over-etching can cause sensor damage and under-etching can lead to poor electrical contact between the sensor and S2. Further, over or under-etching can lead to poor spacing between the sensor and S2, i.e., gap2 thickness control.
It can be seen then that there is a need for a method for providing an endpoint layer for ion milling of top of read sensor having top lead connection and sensor formed thereby.